QHYCCD

QHY268C No Threads on Front Dovetail

QHY268C No Threads on Front Dovetail
« on: February 19, 2021, 08:49:01 AM »
Hello everyone,

I recently purchased a QHY268C-PH and have run into an issue. I expected there to be M48 threads on the front dovetail of the camera as there are on many other QHY cameras, and as there is on the front plate of the ZWO ASI2600MC Pro; however, this is not the case. Because these threads are not present, I must use the CAA, and no longer have enough back focus for specific configurations, which is extremely unfortunate.

Is there something I can do to fix this? The QHY268C manual makes it seem as if there should be threads on the front of the dovetail such that it can be used without the CAA to have a back focal distance of 17.5mm, but this is not the case to my knowledge.

Is their a way to get the full 17.5mm of back focus with the QHY268C-PH?

Thanks,
Ben

Re: QHY268C No Threads on Front Dovetail
« Reply #1 on: February 24, 2021, 02:12:03 AM »
Hello,

I have the same problem, and would be interested in a solution.
How can I use the 17,5mm backfocus?

Thank you,
Stefan

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Re: QHY268C No Threads on Front Dovetail
« Reply #2 on: February 24, 2021, 05:08:59 AM »
Hello

In fact, the 17.5mm rear intercept of QHY268C will not include thread, and M54*0.75mm thread will be included only after the center tilt adjustment ring is used.
However, QHY has a very complete adapter ring system, through the 6 screw holes on the center inclination adjustment ring, you can combine various sizes of interfaces. You can view the combined drawings here.
https://www.qhyccd.com/index.php?m=content&c=index&a=show&catid=193&id=114

Or you can tell me your needs, I can help you recommend the ring to meet your requirements

Re: QHY268C No Threads on Front Dovetail
« Reply #3 on: February 24, 2021, 02:23:57 PM »
Hello

In fact, the 17.5mm rear intercept of QHY268C will not include thread, and M54*0.75mm thread will be included only after the center tilt adjustment ring is used.
However, QHY has a very complete adapter ring system, through the 6 screw holes on the center inclination adjustment ring, you can combine various sizes of interfaces. You can view the combined drawings here.
https://www.qhyccd.com/index.php?m=content&c=index&a=show&catid=193&id=114

Or you can tell me your needs, I can help you recommend the ring to meet your requirements

Thanks for the reply.

It is unfortunate that there is no solution to this problem and that the center tilt adjustment ring must be used. Since the center tilt adjustment ring uses up too much back focus, certain combinations of lens/camera/accessory are impossible with this camera. For example I would like to use the QHY268C-PH with a Canon EOS lens and a filter drawer, but because of the center tilt adjustment ring there is no way to do this.

This is a very large difference between the QHY268C-PH and the ZWO ASI2600MC Pro, since this is not an issue at all with that camera. I would recommend changing the wording under the specifications of this camera, as it seems to imply that it is possible to use this camera without the center tilt adjustment ring (e.g., "If CAA is used...").

Thanks,
Ben

Re: QHY268C No Threads on Front Dovetail
« Reply #4 on: March 30, 2021, 04:09:40 PM »
I agree. The spec of this camera should be changed to "23,5mm backfocus", if the 17,5mm cannot be used. Or can they?

Thanks
Stefan